Systems for administration of fluids to a patient are widely known. The manner of propelling the fluid to the patent may be by gravitation, by means of pressure applied on a deformable container, or by means of a pump. In pump-operated administration systems, the pump must be capable of administering the fluid in a controlled, continuous manner.
Pumps are employed to meet the need for a high degree of accuracy in the administration of fluids, to protect the patient and to maximize the effectiveness of medication.
WO98/46293 discloses the administration of two fluids to a patient. According to this document, a flow set is described which enables sequential administration of two fluids from a pair of containers to a patient. The flow set has a pair of valve assemblies each in communication with a container. Each valve assembly has a chamber; an inlet port sealed with a first one-way valve allowing flow of fluid through it only into the chamber; an outlet port being sealed with a second one-way valve allowing flow of fluid through it only out of the chamber; and a pump port located between the one-way valves. Inlet tubes connect a container to the inlet ports of each valve assembly. A connecting tube connects the pump ports of the valve assemblies to a pump. Outlet tubes are connected to the outlet port of each valve assembly for delivery of the two fluids to a patient. By reversing the pumping direction of the pump, fluid can be sequentially drawn from one container or the other. Generally, a sensor is associated with the pump for sensing when the containers are empty so that when no fluid passes the sensor the pump is switched off and an alarm sounds to alert an operator to the fact that more fluid is required.
This arrangement works well, but it has been found that it suffers from the problem that air entrained in the fluid can be released from solution and sensed by the sensor. This can result in activation of the alarm and switching off of the pump even when more fluid is not required. This is inefficient. Indeed, when the alarm sounds, it generally indicates a) the container is empty and more fluid is required or b) feeding is finished and no more fluid is necessary for this feeding. Thus, when entrained air falsely trips the alarm (often referred to as a nuisance alarm), a nurse may either a) believe that she must renew the fluid supply as more fluid is required or b) falsely believe feeding is finished and no more fluid is required or c) have the experience and sense to check the fluid supply, realize it was only a nuisance alarm and re-start the pump with the same fluid supply (preferably shaking to remove any air bubbles).
Therefore, a need exists for a valve assembly which achieves a good flow and which can be used in the efficient administration of two fluids to a patient, which is safe, relatively simple, easy to use, and requires a single pump. Furthermore, there is a need for a solution to the problem of unnecessary switching off of the pump and activation of the alarm.
The present invention addresses and resolves the problems of the art.